Numerical simulation and experimental analysis of magneto-mechanical behavior of anti-seismic active sandwich structure

This work focuses on the quasi-static behavior study for simply supported sandwich beams with aluminum faces and magnetorheological elastomer core subjected to three points bending subjected to a magneto-mechanical loading by numerical and experimental investigations. The mechanical properties of the magnetorheological elastomer core are measured experimentally and the mechanical behavior of the MRE was identified by the generalized Maxwell rheological model. Depending upon the adjustable properties of the beam, energy dissipation is by core shear. A systematic series of experiments and finite elements simulations have been performed in order to assess the static behavior of the beam. The results obtained show a significant influence of the magnetic field intensity on the flexural displacement of the beam

Vibration control of a hydrostatic bearing using magnetorheological elastomer shell bearing

In rotating machines, random movements or sliding movements of the rotor in its housing can produce undesirable phenomena for some parts. To solve this problem, a new hydrostatic bearing with an intelligent magnetorheological elastomer sell bearing has been designed to control the undesirable vibrations of rigid rotors. The different effects of the influence parameters on the vibratory behavior of the sell bearing are calculated numerically using Abaqus software, and the results found are encouraging

Analyse spectrale des vibrations application à la maintenance des équipements mécaniques

111 p. : ill. ; 30 cmLa surveillance des machines tournantes se fait de plus en plus par l’analyse spectrale des vibrations. Les méthodes d’analyse dépendent de l’organisation des signaux. L’approche classique par la transformée de Fourier (Fast Fourier Transform) est bien adaptée aux signaux essentiellement périodiques. Cependant, elle présente des limitations pour des signaux se caractérisant par des signatures complexes, ou des non stationnarités. A cet effet, l’amélioration de la résolution fréquentielle s’impose, en faisant appel aux méthodes paramétriques, la représentation temps-fréquence (WV) ou la modélisation Auto régressive AR(p). L’objectif de cette étude est de présenter, d’une part, l’outil classique utilisé dans le domaine de l’analyse vibratoire (FFT), et d’autre part, de voir la contribution des méthodes paramétriques auto régressives (corrélation et maximum d’entropie). Les algorithmes de Levinson-Durbin et de Burg ont été testés sur des signaux artificiels ainsi que des signaux recueillis sur banc d’essa

Note on chromatic polynomials of the threshold graphs

Let G be a threshold graph. In this paper, we give, in first hand, a formula relating the chromatic polynomial of Ḡ (the complement of G) to the chromatic polynomial of G. In second hand, we express the chromatic polynomials of G and Ḡ in terms of the generalized Bell polynomials.</p

Numerical Evaluation of Biomechanical Stresses in Dental Bridges Supported by Dental Implants

The number of supporting dental implants is an important criterion for the surgical outcome of dental bridge fixation, which has considerable impact on biomechanical load transfer characteristics. Excessive stress at the bone–implant interface by masticatory loading may result in implant failure. The aim of this study was to evaluate the impact of the number of implants supporting the dental bridge on stress in neighboring tissues around the implants. Results of the study will provide useful information on appropriate surgical techniques for dental bridge fixation. In this study, osseointegrated smooth cylindrical dental implants of same diameter and length were numerically analyzed, using three-dimensional bone–implant models. The effect of the number of supporting implants on biomechanical stability of dental bridge was examined, using two, three and four supporting implants. All materials were assumed to be linearly elastic and isotropic. Masticatory load was applied in coron-apical direction on the external part of dental bridge. Finite Element (FE) analyses were run to solve for von Mises stress. Maximum von Mises stresses were located in the cervical line of cortical bone around dental implants. Peak von Mises stress values decreased with an increase in the number of implants that support the dental bridge. Results of this study demonstrate the importance of using the correct number of supporting implants to for dental bridge fixation